Purpose: In a previous study we noticed that P6 acupressuredecreased postoperative nausea and vomiting (PONV) more markedlyafter discharge. As motion sickness susceptibility is increasedby, for example, opioids we hypothesized that P6 acu-pressuredecreased PONV by decreasing motion sickness susceptibility.We studied time to nausea by a laboratory motion challenge ina group of volunteers, during P6 and placebo acupressure.

Methods: 60 women with high and low susceptibilities for motionsickness participated in a randomized and double-blind studywith an active P6 acupressure, placebo acupressure, and a controlgroup (n = 20 in each group). The risk score for PONV was over50%. The motion challenge was by eccentric rotation in a chair,blindfolded and with chin to chest movements of the head. Thechallenge was stopped when women reported moderate nausea. Symptomswere recorded.

Results: Mean time to moderate nausea was longer in the P6 acu-pressuregroup compared to the control group. P6 acupressure = 352 (259–445),mean (95% confidence interval) in seconds, control = 151 (121–181)and placebo acupressure = 280 (161–340); (P = 0.006).No difference was found between P6 and placebo acupressure orplacebo acupressure and control groups. Previous severity ofmotion sickness did not influence time to nausea (P = 0.107).The cumulative number of symptoms differed between the threegroups (P < 0.05). Fewer symptoms were reported in the P6acupressure compared to the control group P < 0.009. Overall,P6 acupressure was only marginally more effective than placeboacupressure on the forearms.

Conclusion: In females with a history of motion sickness P6acu-pressure increased tolerance to experimental nauseogenicstimuli, and reduced the total number of symptoms reported.

Background: Working while exposed to motions, physically and psychologically affects a person. Traditionally, motion sickness symptom reduction has implied use of medication, which can lead to detrimental effects on performance. Non-pharmaceutical strategies, in turn, often require cognitive and perceptual attention. Hence, for people working in high demand environments where it is impossible to reallocate focus of attention, other strategies are called upon. The aim of the study was to investigate possible impact of a mitigation strategy on perceived motion sickness and psychophysiological responses, based on an artificial sound horizon compared with a non-positioned sound source.

Method: Twenty-three healthy subjects were seated on a motion platform in an artificial sound horizon or in non-positioned sound, in random order with one week interval between the trials. Perceived motion sickness (Mal), maximum duration of exposure (ST), skin conductance, blood volume pulse, temperature, respiration rate, eye movements and heart rate were measured continuously throughout the trials.

Results: Mal scores increased over time in both sound conditions, but the artificial sound horizon, applied as a mitigation strategy for perceived motion sickness, showed no significant effect on Mal scores or ST. The number of fixations increased with time in the non-positioned sound condition. Moreover, fixation time was longer in the nonpositioned sound condition compared with sound horizon, indicating that the subjects used more time to fixate and, hence, assumingly made fewer saccades.

Conclusion: A subliminally presented artificial sound horizon did not significantly affect perceived motion sickness, psychophysiological variables or the time the subjects endured the motion sickness triggering stimuli. The number of fixations and fixation times increased over time in the non-positioned sound condition.

Objective: The aim of the study was to investigate how motion sickness, triggered by an optokinetic drum, affects short term memory performance and to explore autonomic responses to perceived motion sickness.

Background: Previous research has found motion sickness to decrease performance, but it is not known how short term memory in particular is affected.

Results: A total of 16 participants terminated the trial due to severe nausea, while the other 22 endured the full 25 minutes. Perceived motion sickness increased over time in both groups, but less among those who endured the trial. Short term memory performance decreased towards the end for those who terminated, while it increased for the other group. Results from the measured autonomic responses were ambiguous.

Conclusion: The present study concludes that performance, measured as short term memory, declines as perceived motion sickness progresses.

Application: This research has potential implications for command and control personnel in risk of developing motion sickness.

Objective: In this study, possible effects of motion sickness on encoding and retrieval of words were investigated.

Background: The impact of motion sickness on human performance has been studied with regards to psychomotor functions and over learned skills, as well as to novel situations requiring encoding and retrieval skills through the use of short term memory. In this study, possible effects of motion sickness on encoding and retrieval of words were investigated.

Method: Forty healthy participants, half of them males, performed a continuous recognition task (CRT) during exposure to a motion sickness triggering optokinetic drum. The CRT was employed as a measurement of performance and consisted of encoding and retrieval of words. The task consisted of three consecutive phases 1) encoding of familiar words; 2) encoding and retrieval of words under the influence of motion sickness; 3) retrieval of words after exposure.

Results: Data analysis revealed no significant differences in the ability to encode or retrieve words during motion sickness compared with a control condition. In addition, there were no significant correlations between the level of motion sickness and performance of the CRT.

Conclusion: The results indicate that encoding and retrieval of words are not affected by moderate levels of motion sickness. Application: This research has implications for operational settings where professionals experience moderate levels of motion sickness.

Objectives: To establish the prevalence of unsteadiness and rotatory vertigo in peri- and postmenopausal women, and whether balance disturbances are more common in women with vasomotor symptoms and without hormone replacement therapy (HRT). Method: A validated questionnaire was sent to all 1523 women aged 54 or 55 years in Linkoping, Sweden. Results: Daily or weekly unsteadiness was reported by 5%, and daily or weekly rotatory vertigo by 4% of all women. The frequency of vasomotor symptoms correlated with reported unsteadiness (rs = 0.23, p < 0.001). Fourteen per cent of women with daily vasomotor symptoms reported weekly or daily unsteadiness, compared with 3% of those without vasomotor symptoms (odds ratio (OR) 7.58, 95% confidence interval (CI) 3.72-15.45). The frequency of vasomotor symptoms correlated with rotatory vertigo (rs = 0.19, p < 0.001). Ten per cent of women with daily vasomotor symptoms reported weekly or daily rotatory vertigo, compared with 2% of women without vasomotor symptoms (OR 5.21, 95% CI 1.07-25.52). No correlation was seen between vasomotor symptoms and falls. Users of HRT had the same prevalence of balance disturbances as non-users. Conclusions: Women with frequent vasomotor symptoms seem to run a greater risk of unsteadiness and rotatory vertigo than do women without symptoms. This association may not be explained by means of a cross-sectional study, but there might exist a causal connection between vasomotor symptoms and balance disturbances.

Objective: To assess whether estrogen treatment given to postmenopausal women without vasomotor symptoms improves balance more than placebo. Methods: Forty healthy postmenopausal women without vasomotor symptoms were randomized to transdermal 17▀-estradiol (E2) 50 ╡g/day for 14 weeks or identical transdermal placebo patches. Postural balance was measured with dynamic posturography before and after 4, 12, and 14 weeks of therapy. In this test, the visual, vestibular, and somatosensory systems were provoked with increasing difficulty and body sway was measured with a dual forceplate. A low score showed large sway and a score of 100 showed no sway at all. Results: Thirty-eight women completed the study. Both groups had normal balance for their ages and near maximum scores in the three easier balance tests at baseline. In the most difficult test, both groups improved their postural balance significantly (from 13 to 32 and from 22 to 39, respectively) after 4 weeks. Thereafter, no change was seen. One problem was low statistical power, but the relative change in balance did not differ between groups. The comparison did not show even a minute advantage of E2 over placebo, so a study with higher power would probably not have shown a more pronounced effect of estrogen than placebo. The change over time did not differ between groups, which indicates a significant learning effect.Conclusion: In women without vasomotor symptoms, estrogen therapy did not seem to increase postural balance significantly more than placebo. However, we could not rule out that estrogens affect postural balance in women with vasomotor symptoms. Copyright (C) 2000 The American College of Obstetricians and Gynecologists.

Objective: This is a 1 year follow-up to compare the effects of partial tonsil resection using the radiofrequency technique (RF) tonsillotomy (TT) with total tonsillectomy (TE) (blunt dissection). Obstructive symptoms, tendency for infections, and health-related quality of life (HRQL) were studied and compared with the HRQL data from a normal population.

Method: The study group consisted of 74 patients (16-25 yr old) randomized to TT (n = 31) or TE (n = 43) with obstructive throat problems with or without recurrent tonsillitis. The Short Form 36 (SF-36) and EuroQul Visual Analogue Scale were used to evaluate HRQL. A questionnaire investigated the degree of obstruction and history of infections.

Results: Preoperatively, both groups reported significantly lower HRQL in all dimensions of the SF-36 compared with the normal population (P < .05-P < .001). After 1 year, a large improvement (P < .01-P < .001) in both groups in HRQL was found. No differences were found when these groups were compared with the normal population or between the study groups. The effect on snoring was the same for both groups, and the rate of recurrence of infections was low and not any higher in the TT group.

Conclusion: Preoperative obstructive problems in combination with recurrent tonsillitis have a negative impact on HRQL. Both the TT and TE groups demonstrated large improvements on HRQL, infections, and obstructive problems 1 year after surgery, indicating that the surgical methods are equally effective. With its reduced postoperative complications, less pain, shorter recovery time, and cost reduction, TT with RF should be considered the method of choice.

The purpose of the present study was to examine if functional impairment of the skin microvasculature is present in young diabetic patients with and without neurophysiological signs of nerve dysfunction. Dorsal foot skin blood flow was measured in young diabetics and controls using laser Doppler perfusion irnaging (LDPI). Blood flow was- measured during supine resting flow, during change in posture and during post occlusive hyperemia. Peripheral nerve function was measured by electrophysiological studies of peroneal and sural nerve conduction. Fifty seven (57%) percent of the diabetic patients had abnormal nerve conduction in two or several nerves. Diabetics with poor metabolic control (HbAlc > 7,5 %) showed an increase in supine resting blood flow compared to better regulated diabetics and controls. No other differences in skin blood flow between diabetics and controls were seen. During change in posture, blood flow increased instead of decreased in a majority of the study subjects. Low resting blood !low levels are suggested to contribute to this absence of postural vasoconstrictor response. It is concluded that nerve conduction defects arc much more common than microvascular abnormalities measured by LDPI in the present models in young diabetic patients. Our recommendation is to increase basal resting flow before applying vasoconstricting models in yotmg subjects when using LDPI in low flow areas, as the foot skin.

The purpose of the present study was to identify whether young patients with type 1 diabetes using modern multiple insulin injection therapy (MIT) have signs of microvascular dysfunction and to elucidate possible correlations with various disease parameters. Skin blood flow on the dorsum of the foot was measured with laser Doppler perfusion imaging in 37 patients (age 10–21 years, disease duration 6·0–16 years) and 10 healthy controls. Measurements were performed at rest, after change in posture (the leg was lowered below heart level) and during postocclusive hyperaemia. Following a change in posture blood flow increased instead of decreased in a majority of the study subjects. Patients with acute HbA1c >7·5% (n = 22) had an increase in skin blood flow at rest and a significantly reduced blood flow when the leg was lowered below heart level as compared with patients with HbA1c <7·5% (0·26 V versus 0·17 V, P<0·01 and 0·12 V versus 0·23 V, P<0·05, respectively) and healthy controls. Following occlusion of the macrocirculation for 3 min a small non-significant decrease in the hyperaemic response was seen in the patients. The postocclusive hyperaemic response and the venoarteriolar reflex were not correlated to duration of disease, long-term metabolic control or electrophysiological signs of peripheral nerve dysfunction. It is concluded that signs of microvascular dysfunction related to poor metabolic control are present in young patients with MIT treatment and rather well-controlled diabetes. Low resting blood flow levels are suggested to contribute to the absence of postural vasoconstrictor response.

Total sagittal knee laxity and postural control in the sagittal and frontal planes were measured in 25 patients at a mean of 36 months (range, 27 to 44) after anterior cruciate ligament reconstruction and in a control group consisting of 20 uninjured age- and activity-matched subjects. Body sway was measured in the sagittal plane on a stable and on a sway-referenced force plate in single-legged stance, double-legged stance, or both, with the eyes open and closed. Postural reactions to perturbations in the sagittal and frontal planes were recorded in the single-legged stance with the eyes open. Total sagittal plane laxity was significantly greater in the anterior cruciate ligament-reconstructed knee (11.2 mm, range, 6 to 15) than in the uninjured knee (8.9 mm, range, 6 to 12) or in the control group (6.0 mm, range, 5 to 8). In spite of this, the patients, in comparison with the controls, exhibited normal postural control except in two variables - the reaction time and the latency between the start of force movement to maximal sway in the sagittal plane perturbations. This supports the hypothesis that rehabilitation, with proprioceptive and agility training, is an important component in restoring the functional stability in the anterior cruciate ligament-reconstructed knee.

The aim was to assess (i) the test–retest and inter-rater reliability of, and (ii) the relationships between, commonly used clinical balance tests and subjective ratings in subjects with dizziness and disequilibrium. Fifty subjects (26 men and 24 women, mean age 63 years) with dizziness and disequilibrium following acute unilateral vestibular loss or central neurological dysfunction were tested with static and dynamic clinical balance tests, visual analogue scales (VAS), University of California Los Angeles Dizziness Questionnaire (UCLA-DQ), Dizziness Beliefs Scale (DBS), European Quality of Life questionnaire (EQ-5D), Dizziness Handicap Inventory (DHI), and Hospital Anxiety and Depression Scale (HADS). Most tests showed good test–retest and inter-rater reliability. Few correlations were seen between objective and subjective tests, but several correlations were found between the different subjective instruments. Sharpened Romberg's test eyes closed, standing on foam eyes closed, standing on one leg eyes open and walking in a figure-of-eight are recommended as reliable and appropriate clinical balance tests in subjects with dizziness and disequilibrium. Subjects with central lesions may have difficulties when rating their symptoms on VAS. Total scores rather than scores for separate items are recommended for UCLA-DQ and DHI.

Purpose: The aims of this study were to follow recovery during the first 6 months after acute unilateral vestibular loss (AUVL) and to determine predictors for self-rated remaining symptoms. Materials and methods: Forty-two subjects were included less than 10 days after AUVL. Static and dynamic clinical balance tests, visual analogue scales, University of California Los Angeles Dizziness Questionnaire, Dizziness Beliefs Scale, European Quality of Life questionnaire, Dizziness Handicap Inventory, and Hospital Anxiety and Depression Scale were performed at inclusion and at 7 follow-ups over 6 months. Subjects rated their symptoms on visual analogue scales daily at home. Videonystagmography was performed in the acute stage and after 10 weeks. Results: Decrease of symptoms and improvement of balance function were larger during the first compared with the latter part of the follow-up period. Visual analogue scale ratings for balance problems were higher than those for dizziness. A prediction model was created based on the results of 4 tests in the acute stage: standing on foam with eyes closed, standing on 1 leg with eyes open, visual analogue scale rating of vertigo at rest, and European Quality of Life questionnaire rating of health-related quality of life. The prediction model identified subjects at risk of having remaining symptoms after 6 months with a sensitivity of 86% and a specificity of 79%. Conclusions: Recovery mainly takes place during the first weeks after AUVL. Subjects rate more balance problems than dizziness. Self-rated remaining symptoms after 6 months may be predicted by clinical balance tests and subjective ratings in the acute stage.

Conclusions. About half of the subjects in this study reported remaining symptoms 3–6 years after acute unilateral vestibular loss. Differences could be seen between subjects with and without remaining symptoms regarding health-related quality of life, anxiety and depression.

Objective. To evaluate the presence of self-rated remaining symptoms 3–6 years after acute unilateral vestibular loss, and to compare subjects with and without such symptoms.

Material and methods. Firstly, 51 subjects answered a questionnaire which included the EuroQol EQ-5D, the Hospital Anxiety and Depression Scale, the University of California Los Angeles Dizziness Questionnaire, visual analogue scales and the Dizziness Handicap Inventory. Secondly, nine subjects with and nine without remaining symptoms participated in an extended testing procedure, including electronystagmography (ENG), determination of vestibular-evoked myogenic potentials (VEMPs) and clinical balance tests.

Results. In the first part of the study, 27 subjects reported remaining symptoms, 3 reported 1 additional period of symptoms and 21 had not experienced any symptoms at all in the 3–6 years since acute unilateral vestibular loss. In the second part, the group with remaining symptoms rated a lower health-related quality of life and a higher level of anxiety and depression. There were no differences between the two groups in terms of ENG tests, VEMPs or clinical balance tests.

Objective: To evaluate the effects of additional physical therapy on recovery after acute unilateral vestibular loss given to patients receiving home training.

Design: Randomized controlled trial.

Setting: Ear, nose and throat departments in three hospitals.

Subjects: Fifty-four patients (mean age 52 years) with acute unilateral vestibular loss within the last week confirmed with electronystagmography testing were included. Patients with central neurologic or auditory symptoms or other vertigo disease were excluded.

Interventions: Home training with or without additional physical therapy 12 times during 10 weeks.

Main measures: Electronystagmography testing was performed before and after the training period. Clinical static (Romberg?s test, sharpened Romberg?s test, standing on foam and standing on one leg) and dynamic (walking forward and backward on a line) balance tests and subjective ratings of vertigo and balance problems on a visual analogue scale were done one week, 10 weeks and six months after the start of training.

Results: Similar changes were seen in the two training groups.

Conclusions: No significant differences in outcome regarding balance function or perceived symptoms were found between home training with or without additional physical therapy.

Main measures: Electronystagmography testing was performed within one week after onset of symptoms and after 10 weeks. The outcome measures clinical static balance tests (sharpened Romberg's test with eyes closed, standing on foam with eyes closed, and standing on one leg with eyes open and closed) and subjective symptom ratings on a visual analogue scale were done after one week, 10 weeks and six months. The correlation between age and asymmetry of vestibular caloric response, respectively, and the outcome measures were analysed.

Results: Greater caloric asymmetry correlated with poorer performance at the sharpened Romberg's test and standing on one leg with eyes closed at all three follow-ups (rho=-0.31 to -0.54), and with higher symptom ratings at the 10-week and six-month follow-ups (rho=0.30-0.60). Higher age was associated with poorer performance on the sharpened Romberg's test and standing on one leg at all three follow-ups (rho=0.31-0.64), but did not change over time. Higher age was also associated with higher ratings of vertigo at the six-month follow-up, and less reduction of vertigo between the 10-week and six-month follow-ups (rho=0.29-0.48).

Conclusions: A higher degree of asymmetry of vestibular caloric response and high age seem to be associated with poor outcome in balance and perceived symptoms after acute unilateral vestibular loss.

Background: There are several studies indicating a correlation between treatment with hydroxyethyl starch (HES) and pruritus. In order to see whether there is a possible dose–response relationship between HES and pruritus, we retrospectively studied 50 patients who had received HES in varying doses (cumulative dose 500–19500 ml) as hemodilution therapy after subarachnoid hemorrhage.

Methods: Of 50 consecutive patients, 6 were excluded due to severe neurological sequelae. A questionnaire was sent to the remaining 44 patients at 6 months (5–12 months) median (range) after the end of HES treatment.

Results: We received answers from 37 patients, of whom 54% reported pruritus. On average pruritus lasted for 15 weeks. There was significantly more pruritus in patients who received more than 5000 ml of HES versus those who received less than 5000 ml (P=0.023). Pruritus had a delayed onset and appeared as pruritic crises lasting for 2–30 min. It had a patchy distribution in most patients and no predilected locations. In 4 patients (20%) the pruritus lasted longer than 21 weeks.

Conclusion: Our study indicates that there is a dose-dependency for the incidence of HES-induced pruritus, and that in some cases the pruritus may be severe and long-lasting.

Methods of laser Doppler perfusion monitoring (LDPM) and imaging (LDPI) have been validated and found useful for measurements of brain blood flow in several studies. The present work was undertaken to examine the cortical blood flow autoregulatory phenomenon as it has lately been questioned and claimed to be method-dependent and related to sample volume. Spatial variations in cerebral cortical blood flow (CBFcortex) in the pressure range 20–140 mmHg (static cerebral autoregulation; caval block/angiotensin infusion) were studied in six mechanically ventilated (hypocapnic, normocapnic and hypercapnic) pigs anaesthetized with propofol and fentanyl. Although the cortical blood flow values sampled were highly heterogeneously distributed, they were strongly pressure-dependent as well as CO2-dependent (P < 0.001). A cumulative cerebral blood flow (CBF)–pressure (MAP) plot comprising all values obtained indicated a pressure range between 70 and 120 mmHg where CBF remained almost constant. However, at the local level in the cortex (mm2) the same type of ‘classic’ autoregulatory flow : pressure graphs (FPG) were found in only a few of the cases of the cortical areas examined (n = 96). Alterations in blood PaCO2 saturation did not affect the pressure : flow relationship at low perfusion pressures, whereas at normal or above normal values, and as anticipated, hypercapnia considerably increased CBF (P < 0.001). ‘Classic’ autoregulatory FPGs were found only when all values sampled were clustered together, whereas, as a new finding, data are presented indicating that autoregulatory capacity is lacking at the local level at some cortical surface areas.

Background: The ability of the brain to preserve adequate cerebral blood flow (CBF) during alterations in systemic perfusion pressure is of fundamental importance. At increasing concentrations, isoflurane and sevoflurane have been known to alter CBF, which may be disadvantageous for patients with increased intracranial pressure. The aim was to examine the effects of isoflurane and sevoflurane at increasing minimum alveolar concentrations (MAC) on CBF, during controlled hypotension.

Methods: We studied eight pigs during variations in perfusion pressure induced by caval block (100, 60, 50, and 40 mmHg) under normocapnia. CBF was measured locally in a defined area (4 × 5 measurement points covering 1 cm2) of the motor cortex using laser Doppler perfusion imaging. Physiological variables, assessed by analysis of arterial O2 and CO2, hemoglobin and hematocrit, were controlled. CBF was measured during propofol (10 mg × kg−1× h−1) and fentanyl (0.002 mg × kg−1× h−1) anesthesia, and then during anesthesia with either isoflurane or sevoflurane (given in random order) at increasing MAC (0.3–1.2). After a washout period, the measurements were repeated with the other gas.

Results: CBF was significantly higher in the cortex during normotensive (control) settings, MAP ∼100 mmHg, compared with during hypotension (MAP 40–60 mmHg). Neither different anesthetic nor MAC or local measurement sites were found to influence CBF at any perfusion pressure.

Conclusion: In this experimental model, the effect of hypotension on CBF was not altered by the anesthetics used [isoflurane, sevoflurane (MAC 0.3–1.2) or propofol (10 mg × kg−1× h−1)]. In this aspect (cortical tissue perspective), these volatile agents appear as suitable as propofol for neurosurgical anesthesia for patients at risk.

Subjects with neck problems, such as whiplash injuries, often complain of disturbed equilibrium and, in some instances, provocation of the neck position can elicit such problems. The importance of neck proprioceptors for maintaining balance is gaining increased interest, moreover the function or malfunction of the otoliths may disturb equilibrium in certain head positions. The aim of the study was to create a reference material for postural control and its dependence on head position in healthy subjects and to compare this with a set of patients with known neck problems and associated vertiginous problems. A total of 32 healthy subjects (16 men, 16 women, age range 21-58 years) as well as 10 patients age range 27-62 years (mean 44 years) with neck problems and associated balance problems since a whiplash injury were tested for postural control using the EquiTest dynamic posturographic model. The normal subjects were initially split into four age groups in order to estimate the effects of age on performance. The postural stability was evaluated for dependence of support surface conditions (stable or sway-referenced), visual input (eyes open or closed) and head position (neutral, left rotated, right rotated, extended backwards or flexed forward) using analysis of variance (ANOVA) with Tukey's post hoc test in case of a significant factor effect. As expected, visual cues as well as stable support surface improve postural stability (p < 0.001). Postural stability is statistically different in the head extended backwards condition compared with the other four head positions (p < 0.001 in all cases) in both patients and controls. Eliminating this test condition from the analysis, only a slight (p < 0.05) difference between head forwards and head turned left remained. This pattern of results remained if the normal subjects were only split into two age groups instead of four. Finally, the patient group exhibited significantly lower postural performance than all the groups of normal subjects (p < 0.01), but none of the normal groups differed significantly from each other. It is concluded that the postural control system is significantly challenged in the head extended backwards condition in both normal subjects and patients with previous whiplash injury and persistent neck problems. The patient group differed statistically from all groups of normal subjects. This suggests that neck problems impair postural control, and that the head extended position is a more challenging task for the postural system to adapt to. Whether this is due to utricular malpositioning, central integrative functions or cervical proprioceptive afferents is not within the scope of this study to answer. ⌐ 2000 Taylor & Francis.

In patients with unilateral hearing loss and dizziness it is important to rule out a cerebellopontine angle process. This is often done by audiological and otoneurological investigations. However, in many cases we must rely on the imaging of the temporal bone and the cerebello-brainstem area. The paper has presented the three dimensional (3D) Fast Spin-Echo (FSE) T2 weighted, 0.7 mm thick MR images, which in addition to being quick, does not require the use of expensive contrast material. Between September 1996 and November 1997, 152 patients with unilateral hearing loss and/or balance disorders were investigated. In normal cases the 7th and 8th nerves could be followed accurately from the brainstem to the internal auditory meatus. The found tumors were hypointense compared to the cerebrospinal fluid and could be outlined with reasonable accuracy even without gadolinium contrast. The inner ear had high signal, like cerebrospinal fluid. The patency of the cochlea could be estimated accurately. Thus, 3D FSE T2 weighted images can reliably differentiate between patients with and without pathologies of the cerebellopontine angle. The use of gadolinium contrast could be avoided in most of the cases, but contrast is necessary for differential diagnostic purposes in patients with alterations in the cerebellopontine angle or in doubtful cases.

Equilibrium assessment by means of posturography can be performed ina dynamic fashion, meaning that the environment does not remainstable during the test. In the EquiTest dynamic posturography version, the support surface and the visual surround are movable, actively or in response to body movements. Equilibrium ability is investigated in a sensory organ1zat1on (SO) part where six different combinations of vision (normal, sway referenced and absent) and support surface conditions (stable and sway referenced) are given. Postural responses to sudden translations and tiltings of the support surface are investigated in a movement coordination (MC) part.

standardized dynamic posturography was utilized to assess equilibrium performance in different groups of subjects. In twentynine elderly healthy subjects, dynamic posturography evaluated the influence of age on equilibrium parameters. A decline compared to younger age groups was f~und. Fifteen of the elde:ly s~bjects underwent physical exerc~ses two hours a week dur~ng n~ne weeks, the remaining subjects served as controls. Significant improvement attributable to the exercises was found in one out of six so conditions and two out of twelve clinical equilibrium tests. In twenty-eight subjects with polyneuropathy, impaired equilibrium was found in so and delayed reactions to sudden support surface movements -w~re found in MC. Comparing dynamic posturography with neurological measures of polyneuropathy unveiled correlations between subjective clinical scoring and latencies to forward translations in MC and to equilibrium performance in three out of six so conditions. In seven subjects with chronic toxic encephalopathy due to industrial solvent exposure, impaired equilibrium was found in four out of six so conditions, although MC was normal. In thirteen healthy subjects, acute low level alcohol ingestion caused balance disturbances in SO conditions with abs7nt visual cues. In addition to disturbances of ocular smooth pursu1t and visual suppression of the vestibuloocular reflex in elevenabstinent chronic alcoholics, deteriorated equilibrium performance was found in four so tests out of six. Postural reactions to both sudden translations and tiltings of the support surface were found to be marred, in spite of normal nerve conduction velocities.

The EquiTest dynamic posturography apparatus was cont:olle~ by amenu-driven interface constructed at the department, ~n wh~ch the user may expose the subject to arbitrary movement~ ~f the.supp~rt surface and the visual surround. The effects of v1s1on, d~rect~on and amplitude on postural reactions to su~den support surface translations were evaluated. Absence of v1sual cues caused more rapid correction maneuvres, but the translation direction did ~ot influence the reactions. Postural responses reflected translat1on amplitudes.

One of the main issues for balance control is the ability to generate enough forces to execute motions and uphold stability. This study aimed to investigate whether induced fatigue of the triceps surae muscles and decreased muscle force due to temporary additional body weight affected the ability to withstand balance perturbations. Another aim was to examine whether postural control adaptation over time was able to compensate for the changes induced by fatigue and additional body weight. Eleven normal subjects were exposed to vibratory proprioceptive stimulation during three test conditions, a baseline test during normal condition, when the body weight was increased by 20%, by adding additional weight load, and when the triceps surae muscles were fatigued. The tests were performed both with eyes open and closed. The body movements were evaluated by analyzing the anteroposterior and lateral torques induced towards the supporting surface measured with a force platform. Postural control was substantially affected both by the additional body weight, and by muscle fatigue in the triceps surae muscles. The anteroposterior and lateral body sway were larger both with added weight and fatigued muscles compared with the baseline test during quiet stance. However, the body sway induced by the vibratory stimulation was significantly larger with additional body weight compared with when the triceps surae muscles were fatigued. The differences between the test conditions were mostly pronounced during tests with eyes closed and in the high frequency body sway (>0.1 Hz). Postural control adaptation was able to reduce but not fully compensate for the changes induced by fatigue and additional body weight. Several hypotheses could account for these observations. (1) Fatigued muscles are less sensitive to muscle vibration, (2) muscle fatigue alters the muscle contractile efficiency and thus alters the ability to produce high-frequency, short-latency responses to balance perturbations.

Objective - Several reports have shown that the direction of the postural responses induced by vestibular stimulation is affected by the positions of the neck and torso. The aim of this study was to investigate whether the postural responses to vibratory proprioceptive stimulation of the calf muscles are affected by the position of the head and thus by proprioceptive and vestibular information from the neck and head. Material and Methods - Ten normal subjects were exposed to vibratory proprioceptive stimulation of the calf muscles when the head was maintained in five different positions: in a neutral position facing forwards, with the head turned to the right or left sides or with the head tilted backwards or forwards. Body movements were evaluated by analyzing the anteroposterior and lateral torques induced towards the supporting surface. Results - The analysis showed that only the anteroposterior body sway was significantly affected by the position of the head. The anteroposterior postural responses were primarily increased during the tests with the head tilted backwards or forwards, whereas the postural responses were unaffected by head torsion towards the sides. The lateral responses were primarily affected by vision and not by the position of the head. Conclusions - The findings suggest that the responses evoked by vibratory proprioceptive stimulation of the calf muscles may be affected by different mechanisms, either by purely proprioceptive information or by an interaction between proprioceptive and vestibular information. Moreover, the increasing difference between the test conditions over time suggests that fatigue of the neck muscles may be one of the factors affecting the responses induced by the perturbations.

Dizziness and disequlibrium2010In: Physical activity in the prevention and treatment of disease: Professional Associations for Physical Activity, Stockholm: Swedish National Institute of Public Health , 2010, p. 356-366Chapter in book (Other academic)